PURPOSE: To acquire sufficiently a back metal and prevent the chipping of a cutting edge by providing a flank formed with a smoothly curved surface where clearance angles become larger continuously from the cutting edge side at a broach toward the axial rear.

CONSTITUTION: In the case of a broach 7 that is one kind of cutting tools, when the flank 2 of its one cutting edge 1 is formed with a smoothly curved surface, its clearance angles are made to become larger continuously from a clearance angle a0 at a position near a cutting edge 1 to a clearance angle a3 at a position near a heel. And as for a rough edge portion and a middle finish edge portion, a0 is made to be in the extent of 1-3°, and a3 is made to be in the extent of 2-5°. Also, as for a finish edge portion, a0 is made to be in the extent of 0-15°, and a3 is made to be in the extent of 30°-2°. When the flank 2 with such a curved surface as above is subjected to grinding processing, a cup shaped grinding wheel 3 is used, and the flank 2 is ground by rotating the cup grinding wheel 3 with an inclination angle θ in regard to a rotary shaft 4 and by means of the inner periphery edge 6 of its bottom surface 5.